Primary cilia and Gli3 activity regulate cerebral cortical size

Area of Science:

• Neuroscience
• Developmental Biology
• Cell Biology

Background:

• Neural development involves coordinated regulation of patterning and neurogenesis across brain regions.
• Primary cilia are increasingly recognized for their roles in developmental signaling pathways.

Purpose of the Study:

• To investigate the necessity of primary cilia and Gli activity in normal cerebral cortex expansion.
• To elucidate the molecular mechanisms by which primary cilia influence cortical progenitor cell cycle kinetics.

Main Methods:

• Utilized Kif3a knockout models to study the effects of primary cilia loss.
• Analyzed cell cycle kinetics, gene expression (cyclin D1, Fgf15), and protein levels (Gli3) in cortical progenitors.
• Examined the impact of altered Gli3 activity on cell cycle progression and molecular markers.

Main Results:

• Loss of Kif3a led to primary cilia degeneration, significant cerebral cortex overgrowth, and altered progenitor cell cycle kinetics.
• The G1 phase of the cell cycle was shortened, associated with reduced Gli3 activity, increased cyclin D1 and Fgf15 expression.
• Altered Gli3 activity alone mimicked the cell cycle acceleration and molecular changes observed in cilia-deficient brains.
• Full-length and repressor Gli3 protein levels were tightly regulated during development, correlating with cyclin D1/Fgf15 expression and normal cell cycle lengthening.

Conclusions:

• Primary cilia and Gli activity are essential for regulating cerebral cortex size.
• Gli3 activity, modulated by primary cilia, controls cell cycle length in cortical progenitors, thereby determining cortical size.